Biochemische Aspekte des Alkoholismus

Abstract

The use of alcohol in our societies has many social and economic consequences and the abuse of this drug leads to various alcohol-related disabilities. As a result, research is warranted which will lead to a better understanding of the parameters underlying alcohol use and abuse. In recent years biological research has yielded much knowledge regarding the effects of ethanol on the body. Direct effects of the unmetabolised molecule are observed on the cell membranes, particularly of the central nervous system. Normal metabolism of ethanol occurs mainly via oxidation by alcohol dehydrogenase (ADH) present in the liver, which produces acetaldehyde and reduced coenzyme. The total activity of ADH in human liver varies considerably due to the occurrence of isoenzymes and of a genetic polymorphism. One variant enzyme, called “atypical”, leads to higher ADH activities. Individuals carrying this variant show a slightly faster alcohol metabolism, leading to higher initial acetaldehyde concentrations in blood. Acetaldehyde is quite toxic and can provoke symptoms such as flushing, tachycardia and nausea. “Atypical” ADH prevails in Mongolid races, presumably leading to the frequently observed hypersensitivity to alcohol in Orientals. Only 3-20 % of individuals in Caucasian populations are carrier of the “atypical” enzyme and accordingly signs of hypersensitivy occur less frequently. Hence, the genetically determined enzyme patterns may represent an aversive factor with regard to alcohol consumption. On the other hand, regular intake of alcohol in spite of the unpleasant consequences may lead to an increased organotoxicity due to acetaldehyde in individuals with the “atypical” variant, as compared to “normal” individuals.